Sunday, May 29, 2011

Sunbox curves to Degree Days and PV combined

29 May '11: I have been comparing the Sunboxes over the year with the PV and the Degree days.
   It's annoying that February is a month of 28 days sandwiched between two of 31, because that always caused a blip in curves.
   The PV is performing the same as a year ago, the Sunboxes are gathering more per month than a year ago.

The curve reveals that as we pass the Equinox, the PV and SB curves swap positions. That is for two main reasons,
• Between 1st October and and of April, the GSHP is providing some heating to the house, so the delta-T improves and the SBs work more. This is also the explanation supported by Chris Wood.
• As the sun angles go past the Equinox, the effect of the two hills south of the house come into play, reducing the sunshine hours in winter by delaying sunrise and advancing sunset. So the PV capture is reduced more than if we were on flat ground.

More reflections on these curves:
• The air temperatures are still relatively warm in the boundary months of October and April, improving their performance further in those two months, so May dips below April in both years.
• Colder air temperatures but high sun angles in May seem to be beneficial for the PV capture. Following that thought, it is alarming how much the PV performance drops off in July and August when the panel surface temperatures get so high.
• When the sun is really high in June, there is a lot of reflection off the front face of the panels, and the thermal capture is more helped by long hours of warm air temperature than by direct sunlight. At this time, it might be better to open the vents and let the air in, rather than let the black chillers cool the space.

Reflection on Geometry and Mirrors:
• I wish I had not been so neat and tidily determined to stay within the 200mm sizing of the boxes, resulting in vertical front sunbox faces. Any angle would have been better, to reduce summer sun angle reflection - say 85-75º (5-15º from vertical). This was the idea in the Sunbox mark 2 that I built last year, but never erected onto the wall. See illustration, right.
• With a better sloping angle, there would be no need for the foot mirrors - their effect is to simulate a sloping front face by enlarging the angle of incidence to the sun. The top mirrors seem to have been effective in the winter months, but do nothing in summer.
• I have tilted the foot mirrors of the existing sunboxes to have a reverse camber - really tilting the midday sun right into the box. All I need now is some midday sun!

Friday, May 27, 2011

Key performance indicators

Key performance indicators:
1. GSHP effort related to degree days
2. Deep ground Temperatures
27 May '11: We have had real problems getting information out of the old datalogger (below), so I am dependent on the many meter readings of the last 2 years. Blaise had to reboot the datalogger - the memory was full and it wasn't releasing the information it had. I might have to buy some USB ones.

Meanwhile, above are two key performance indicator diagrams which I needed for my SET 2011 article.
Left: The comparison of Degree Days in Nottingham (Red, indicating the level of space heating required) and the workload of the GSHP for heating (Blue curve, in kWh/month) This indicates that the GSHP worked with less electrical consumption even though the winter was more severe in Nov-Dec 2010.
Right: The deep ground temperatures measured since August 2009. My measuring method now is very rigorous, with fewer ups and downs than in 2009. But the smoothed trend is very visible, with the ground temperature falling to 5º in Winter 2009-2010 and only falling to 10º in Winter 2010-2011.

Wednesday, May 25, 2011

May 2011 Reports

Every Sunday evening, I take meter readings and compute the annual consumption and generation figures. 

29 May 2011: The last week has been mostly cloudy, and PV figures have been poor. The house total and the GSHP total are again lower than ever, with 5,316 and 3,340 kWh respectively. The Sunboxes have been very quiet because air temperatures are moderate but not hot, and the GSHP using less than an hour a day of power for water heating.  The PV is getting close to the 5,000 kWh line (since installation in Oct 2009).

22 May 2011
I've been away most of the week, in Prague for the Isover world final. But it was a sunny week, and the family were still here. As with the previous weeks, the Annual consumption just got better again, still lower than last week. At this time of year, consumptions are so low due to it being Summer that progress slows down. One bad day in the Winter is equal to an entire week in the Summer. Daily incremental gains or losses in Summer are too small to take seriously. So, let's enjoy it for now, and recognise that I will really know if this is proven by seeing the Winter performance in 2011-12. Ground temp is the highest this year, at 12.7º, but with reasonable sunshine and little use of the GSHP. I am disappointed that it is not over 13º by now. Patience, friend, patience!

Postscript 2.1.2012: Isover have published the student work on a website Another point is that at this time in May, I expected the figure of 5,300 and 3,300 to be the incompressible lowest annual consumption figure, but postscript writing on 2 Jan 2012, the figures are 4,650 and 2,650 respectively!

15 May 2011
It has been a colder and less sunny week, but the same week last year was cold, so our system continues to break the record. This can't continue, but let's enjoy it while it lasts. It will level off when the effect of the mirrors have worked through the system, and if the autumn quarter of 2011 is warm, then the consumption figures will reduce even more!
• House electrical at all time low of 5,330 kWh
• Heat Pump consumption at all time low of 3,350.5 kWh
• Sunbox capture all time high of 3,091 kWh
• The PV power seems to generate an average of 3,280 kWh, oscillating between a worst of 3,236 and best of 3,322. There is no prospect of that changing as the number of panels are at their optimum.
• The Ground temperature is 12.4º. A year ago it was 11.7º, sometimes touching 12º.
Summary: I didn't expect the House to go below 5,600 kWh/yr and the Heat pump to go below 3,600 kWh/yr, and I hoped the Sunboxes would achieve 3,000, and I might have settled for those figures. But they have done better than all of those and they keep getting better! I would have hoped for a higher ground temp than 12.4º, it is only slightly higher than the same time last year - although at this time, the SBs had already been working for 2 months.

8 May 2011
Weather: Although the hot weather has broken - plenty of rain last night, the temperatures are still warm and the garden is blooming with seedlings and green shoots from things which seemed to have died in December's frost. Amazing how the botanical world can tell the difference between real rain and water from a watering can. Seeds are shooting up in the last two days after a month of sitting tight underground. This fine weather has certainly helped to make our figures look better than if this Spring had been identical to Spring 2010.
   As for the solar and heating data... more records being broken as usual. Annual totals are recomputed every Sunday, so how's it looking?
• The house electrical has plummeted downwards through the 5,400 kWh barrier (it was 6,300 kWh last December, and averaged at 8,500 kWh in the two years preceding this project) This takes into account the greater economies of the heat pump being augmented by the Sunboxes, and the benefits of the PV roof which must be contributing about 2,000 kWh per year. Although it generates 3,250 kWh a year, my estimate is that we are using 60% of that, not 50%.
• The heat pump consumption has plummeted through the 3,400 kWh barrier. This includes the space heating, DHW and Underfloor circulating pump. Only a bit more and we can close the circle - to meet the PV power generation of 3,300 kWh.
• The Surya Sunboxes heat buried during the year has risen to an annual figure of 3,070 kWh. There is no space heating at this time, so this is entirely due to general sunshine and a tiny amount of GSHP demand when hot water is needed. The birds and atmospheric dust are making the foot mirrors dirty, so I did a bit of cleaning yesterday.
• See

Paper emerging for Istanbul

25 May '11: I'm working on a conference transaction paper about the Surya Sunboxes - it's for the conference in Istanbul Sept 2011. I don't know if this will ever get finished as I am nearing a deadline and still have things to do on it.
   One thing I am lacking is results at the engineering level. My meter readings prove that there has been a massive performance benefit, but some of that is due to good weather. Only data from sensors can really prove this. I never have managed to get useful datalogger information due to malfunctions with it and with us (memory filling up, Blaise's software being unable to find it, etc) and am grateful that my daily meter readings have been so persistent and accurate. They have been able to give me many useful readings and material for graphs.
   From my many meter readings, I compared some numbers for the time between March 15 and May 24, for 2010 and 2011.
GSHP PV Sunbox
2010 520 961 683
2011 286 994 775
There are two significant differences here, one is the milder spring weather of 2011 giving the GSHP less work to do. The other is that during this year, the sunboxes have had reflectors and last year they did not.
   I will modify this table at the end of May, and at the end of June.
   The performance of the Sunboxes is paradoxical because when the weather is colder, the GSHP works harder and gets more heat from the SBs. During sunny spring days, the SBs tick over at the slow pumping rate. The highest daily SB harvest appears to be on very cold but sunny spring or autumn days.
31 May 2011 Postscript: The final version of the article has been uploaded now to the SET 2011 website.

Monday, May 23, 2011

Prague winners.... nearly

22 May 2011: I've returned from Prague where we were competing in the world final of the Isover Student competition - three schemes from Nottingham University representing the UK, and all capable of operating the building with zero carbon emission in the residential parts.
   There seemed to be two types of schemes, ones that were well worked through like ours, with details of every part of the building, construction, thermal strategies etc. There were some which seemed to be a one week 'Ideas competition for New York' projects, with schemes that were more public art sculpture than building. Some of these had been done in a week last month, but ours was started in September 2010.
   Our best design came FIRST in the first category, but was second overall: overall winner was given to a scheme that was a public art project, a lit up cuboid (like an illuminated Seagram Tower) with no section, no construction, no facade, no plans better than 1000th, no bioclimatic strategies or passivhaus verification, a glass box that was like something from Dubai - the whole thing a piece of Photoshop trickery - and it omitted the new World Trade centre buildings from the renderings.
  I disagree totally with this, as the competition was called the Multi-Comfort House competition, and we took this title very seriously. I've checked on the conditions and they ask for an 'integrated' view of design, which to me suggests that a mere concept is insufficiently complete. Shame on the very small and undistinguished jury for making this judgement.
  The UK competition had a timetable that included three clear stages, with the 3-day long exhibition at Ecobuild displaying the designs to the largest possible audience. With the quality of the organisation and of the judges, I would say that Isover UK conducted the process extremely well.

I will post a photo when I get it out of the camera

Tuesday, May 17, 2011

Open Days in West Bridgford

15 May 2011: During the Summer Gathering of 14th May, people were able to sign up to visit some houses during the Open Day for the West Bridgford Ecohouses group. Several houses were open for a couple of hours during Sunday to demonstrate eco ideas - garden sharing, external insulation, eco renovation, woodburning boilers, PV, and my GS heat pump with the Surya sunboxes.
  As there were several other houses demonstrating PV, I was happy that the majority of questions were about heat pumps.
  Sorry, I forgot to take a photo when the majority of people were here, but remembered when the second group were here.
  My other sorry is that I wanted to post a preview of the Open Day in case any of the Blog-readers would like to turn up, but on Friday before the event, Google-blogger was suspended for maintenance, so we could not add or modify pages.

Tuesday, May 10, 2011

GT11 Sensor replaced

9 May '11: Had a surprise visit today from Derek, the roving Ice Energy engineer. I have long complained to IE that my outgoing sensor (GT11) was becoming increasingly erroneous, and has recently been showing as 10ºC higher than it really is. The GSHP is not malfunctioning particularly, but with my ongoing project, it is damaging data collection to have a very important sensor displaying wrongly. I cannot measure delta-T between outgoing and incoming glycol.
  My job card must have risen to the top, somehow.
  So he replaced it with a new sensor, in a better position (where it is accessible in future) and did a check over of operating parameters, and cleaned the filter on the ground loop and heating loop. He seems very interested in the modifications I and David Atkins have made to it, but I wish the management of IE would show interest too.

Sunday, May 8, 2011

Top flashing fixed!

7 May '11: On the day that Nottingham Forest make it to the nPower Championship playoffs by beating Crystal Palace away by 3-0, I sorted out my airgap problem.
A. LH sunbox half flashed / B. RH sunbox completely flashed
There is a gap at the top of the Sunboxes, the thickness of a finger. I guess that it is letting too much hot air escape as it is right at the top and hot air rises.  I have been wondering whether to fill it with foam, or rope or hosing..... or what...? I want it to be compressible so that the rooflets can still tilt upwards, but it has to be durable enough to not need replacing every year.
  I realised I had some self-adhesive Flashband in the garage. I worked out a simple detail with this that would glue to the polycarbonate and to the aluminium, and yet allow rainwater to escape sideways - and make it completely airtight along the top. I tried it with a short section of the self adhesive flashing, and it went in sweetly and sticks firmly to the two materials. So then I finished the lot - moving the ladder along, and using a harness to make sure of safety.
  The picture A is of the right hand box, with the unflashed part in the foreground and the distant part having had flashing applied. The picture B is of the left hand box, completely flashed now. This photo is taken looking along the space behind the top mirrors. 
  There are gaps at the bottom, and I might just use some duct tape for this, as a short term fix.
22 May Postscript: Forest didn't get further than the playoffs, a goalless draw with Swansea at home and a 3-1 defeat at Swansea's ground...

Thursday, May 5, 2011

Air Gap along the top

Early diagram trying
twin mirrors at foot
5 May '11: I Climbed the ladder to re-fix the aluminium cover to the outlet pipes, but while up there realised that there is an airgap at the top the thickness of a finger all the way across the top of both boxes. 
   In the section the airgap is behind the upper mirror, so perhaps rain is able to run down the back too.... Rain? What rain? we haven't seen any since March!

When building the boxes I had the idea that ventilation of the boxes would help, but as I have used them for over a year, it has become apparent that for the greatest part of the time, they are better being airtight. They never overheat, the temperature gets to a maximum of mid forties, and that is quite safe - as long as the black chillers work, they are drawing heat away and this never exceeds low twenties, because the heat is being dumped.
  I am not sure what the sunbox air temp would be if I turned the pump off on a very hot day. If there is a temporary shut down due to a faulty pump, energy meter or thermostat, it could go up to 50º but I have vents top and bottom to release the heat.
  I will try to source some compressible foam to put up there, and then check the resulting temperatures. A more permanent fix would be some thin gauge aluminium to put across the gap. 
   This section through the boxes shows the upper mirrors, and their 60º angle. Ignore the lower mirrors, I decided after the upper ones worked well to make the foot mirror simpler and single. The dotted blue lines in the diagram illustrate the solar midday angles for summer, equinox and winter.

Tuesday, May 3, 2011

Why use Sunboxes?

3 May '11: Lyndsey (writing a dissertation about the Peveril Solar house) brings me back to one of the fundamental questions : why have a Sunbox at all? 
Dr Chris Wood believes that we could use black chillers nakedly on the wall or roof - he is building a test rig in Burton on Trent using the same black panels as on the Peveril Solar House, but is omitting the glazed boxes. His intention is also to charge the ground.

So why enclose? Well, we could use unglazed black chillers and with enough of them, they could partially or completely take the place of the ground, making the GHSP into an Air source. But for this to happen they would be coated with Ice for much of the winter because they could benefit from the latent heat of freezing and thawing. But I believe that they would be prey to all the faults that ASHPs have in winter. The pipes running through the house would be dripping with condensation every metre along the way, and the GSHP would have to work hard to get the loop temperature low enough for form that ice.
Using Sunboxes, we are still reliant on the ground as our primary source and battery, but we are now making the ground less reliant on itself - it gets actively recharged all the year round instead of just in the summer in a very slow natural way. During the winter of 2010-2011, the deep temperature never went below 10 degs.
The Sunbox system is a warm, not icy, form of augmentation. The thermostatically controlled pump ensures that it is never wasting energy pumping for futile or marginal benefits - when there is no warmth to collect, it turns off!

Monday, May 2, 2011

Degree days in April 2011

This graph has the hot water and
underfloor heating pump omitted.
2nd May Postscript: 2nd May brought us over 25 kWh of PV power and I can only put this down to the very cold east wind that must have been cooling the panels efficiently. The sun was the same for both days. The strong sunshine is warming the house so well that we are still not turning on the heating, even in the evening - there's enough residual warmth to last the night.

Degree Days in April
Now that April is done I see that the degree days for the month was 126, compared with 198 in 2010, in fact that is lower than for May or October of last year, it has been the hottest April of the century! No wonder our GSHP consumption has been so low.

Forest Fires?
No, I am not talking about Nottingham Forest's chances of promotion to the Premier league. Now that we hear of these gorse fires everywhere, we are getting close to the sort of danger that happens in other countries with long drought, that of fires.
    There were kids lighting a campfire in the wood on the hill above the house, and I didn't feel I could say something about it, not just because of the aggro, but most of the campfires held up there have so far been non-harmful apart from the binbags full of glass and cans that the forestry group have to tidy away at the end of each month. Would they take any notice of posters up there asking people not to have fires until after the drought ends?

1st May update PV and Meters

1 May '11: Aaah, the Wedding hangover.... and my daughter cycled 150 miles during the wedding and a couple of days after - pity she wasn't connected to a dynamo! Cycling to Cambridge during the wedding wasn't a tribute to the new Duke, as his title was announced after the ride started.
    Today we had a record Photovoltaic harvest for this time of year, 24.20 kWh, even though it is still 7 weeks before the Summer Solstice. This is explained by the ultra clear sky, but also by the very nippy North East wind that helped keep the panels cool all morning. There were two days with scores of over 24 kWh in a day during May 2010, so this is a good start. But really.... I wish for a day of heavy rain to water the garden and all the other gardens!
    However, all is not perfect, each of Feb, Mar and Apr 2011 have gathered lower PV figures than the same months of last year, and maybe I should get 'Brian' in to clean them with his long brush! (or do it myself.). With only about 10 mins of rain in the whole of April, surely it should have been a higher PV harvest?
  On the metering front, things are still going well. The house meter is about to dip below 5,400 kWh for a whole year, and the Heat Pump is about to go below 3,400 kWh. (This heat pump figure includes the Heating, Hot water and Underfloor circulating pump). The Surya Sunboxes have had a good week despite the dormancy of the heat pump, and they have scored 3,030 kWh for the last year.

TV Aerial shadow: One annoyance is bothering me which is that the summer afternoons have a distinct 300W dip in the Bell Curve while the shadow persists - this can be seen above from 3pm till 4.30pm when the Sun is finally around to the West. Any shading on the entire array will cause a loss.
  This doesn't need shifting sideways. I think the vertical tube is held in a clamp, and can be moved downwards.

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